Modern hybrid vehicles often have a start/stop equipment by means of which the engine of the hybrid vehicle is stopped as soon as the hybrid vehicle stops longer than a predetermined time period (for example 1 second) to thus save fuel. As soon as the driver subsequently actuates an accelerator pedal of the hybrid vehicle, actuates the clutch or selects a gear, the engine automatically restarts to further power the hybrid vehicle. Furthermore it is common in modern hybrid vehicles comprising an internal combustion engine and an electric engine that the internal combustion engine of the hybrid vehicle is started automatically under certain conditions, in particular when the hybrid vehicle detects that the charging state of its battery is below a predetermined threshold value.
This automatic start-up of the engine, however, besides the previously mentioned advantage of saving fuel also has a risk potential which is not negligible, since it is not desirable in certain situations that the engine is being started, for example when an infant, who is playing in the hybrid vehicle, actuates the acceleration pedal while playing or when certain maintenance work is carried out in the engine compartment, for example.
It is known from DE 102 11 463 A1 to monitor the state of the engine hood of the vehicle in a hybrid vehicle and in the case that an opening of the engine hood is detected to disable a start-up of the internal combustion engine.
However, this approach is associated with the problem that, in the so-called ready-to-drive or electric mode, in which the internal combustion engine is not yet started, the vehicle may break down in the case of a defective engine hood sensor since no start-up of the internal combustion engine is possible in this case.